The present invention relates to amplifier circuits. More particularly, the present invention relates to a current leakage compensation circuit and method for providing a reference current to an amplifier circuit.
The increasing demand for higher performance amplifier circuits has resulted in the continued improvement of the precision and accuracy of the various devices and components within the amplifier circuits, as well the inclusion of additional buffers and compensation circuits.
In the implementation of various amplifier circuits, losses in the integrity of referenced currents flowing through the various devices and components can be realized. As a result, the delivered current can be possibly more or less than the intended current to the amplifier circuit. The cause of current losses can be greatly attributed to the presence of current leakage elements as well as parasitic processing components/elements occurring within the circuit devices.
The current leakage elements most often comprise diodes, created by the N and P regions, of the transistor devices within the amplifier circuit. For example, with reference to FIG. 1, a circuit 100 comprising a differential pair of transistors Q1 and Q2 as may be used within a logarithmic amplifier circuit are illustrated. A first reference current IC1, is provided to the collector of transistor Q1, while a second reference current IC2 is provided to the collector of transistor Q2. However, instead of currents IC1, and IC2 flowing through transistors Q1 and Q2, leakage currents ILEAK1 and ILEAK2 created by the N1/P1 and N2/P2 regions at the diode junctions are realized, i.e., leakage current flows from the N region into the P region. This loss of integrity in the referenced currents results in currents IC1xe2x88x92ILEAK1, and IC2xe2x88x92ILEAK2 flowing through transistors Q1 and Q2, which results in less accuracy during operation.
Accordingly, a need exists for addressing the leakage current resulting within devices and components of amplifier circuits.
In accordance with various aspects of the present invention, a leakage compensation circuit and technique is provided that compensates for losses in a referenced current of an amplifier circuit due to leakage elements. The leakage compensation circuit is configured to inject current substantially equal in magnitude to the leakage current into one or more junctions of the amplifier circuit to compensate for lost referenced current due to leakage. As a result, the amplifier circuit and various devices can realize the flow of the reference current as substantially intended without detrimental effects of leakage current, thus maintaining the integrity of the referenced current.
In accordance with an exemplary embodiment, the leakage compensation circuit comprises an array of compensation regions. The array of compensation regions is configured to approximate the collective loss that is created by the leakage elements and provide a compensation current substantially equal in magnitude to one or more junctions to compensate for lost referenced current. To facilitate the injecting of compensation current, the leakage compensation circuit can comprise a current mirror circuit for providing the compensation current to the amplifier circuit.